Depth of field and crop factor misconceptions.
ฝัง
- เผยแพร่เมื่อ 30 ก.ค. 2024
- There is still a lot of incorrect information out there about -
-Depth of field
-Crop sensor vs full frame cameras
-Speedboosters
-Light refraction
And it seems many people who profess to know all about their camera gear, don't actually fully know some of the basics regarding-
-Aperture
-Focal length
-The focus plane
-Crop factor
-The Circle of confusion
-ISO
-Image noise
So I decided to talk about all of the above, and I drew some simple illustrations for you, and also took a few photos to help show what is actually happening to the light as it travels through our cameras lens.
I really hope this video is useful.
P.S. Please see the pinned comment below for a list of minor mistakes. (TH-cam has changed annotations, so i couldn't add those over the video.)
In addition. here is a download zip of the out of camera photos from full frame and M43 once the CF equivalence is done correctly. - dl.dropboxusercontent.com/u/9... - วิทยาศาสตร์และเทคโนโลยี
![Depth of Field Explained: Ultimate Guide to Camera Focus [Shot List Ep. 4]](http://i.ytimg.com/vi/ZGNUqNFfD8M/mqdefault.jpg)
![BOWKYLION - เจ้านายคะ (work-life imbalance) [Official MV]](http://i.ytimg.com/vi/6bFj8G2pOi4/mqdefault.jpg)
Hi guys! I just uploaded a FOLLOW UP VIDEO, that handles some criticisms about this video.
Also flags a couple of small mistakes i made within this vid.
Link-
th-cam.com/video/fCIWkqcb7FI/w-d-xo.html
biscuitsalive nice videos, this is how you should learn photography! Please recommend books!
biscuitsalive
I'm very glad that I learned something from your video. but pardon me. the DOF diagram illustration is showing in your vedio, from my point of view, after the rays refracted through the lens, the focus circle of further object should be on the Focus Plane's left . Because this point circle gives a narrow angle, thus, the rays though the convex lens can give a easy refraction. Therefore, the focus circle should be on the left of the Focus Plane. Hope I can get your feed back. cheers.
@@yongchaozhao8449 If you mean the magenta dots and lines that appear at about 8:43, you are correct. When the object point moves further from the lens, the image point moves closer to the lens. The video's author does know about the error, and corrected it in his follow-up video.
holy crap! 4 years of film school, numerous shoots, a ton of bro camera science and only now i finally get it, thanks!
This is the most complete explanation of this yet, been trying to fully understand this for years. Thanks!
Billy nice one Billy! Glad it was useful.
Thank you for doing this video. It is hard to find knowledgeable sources for this on the internet. Most people have the “camera for dummies” version of this where it only goes as deep as “iso bigger=brighter” and “aperture smaller number = brighter.” So thank you for explaining the why of it instead of patronizing me with fairly common camera knowledge. 🙏🏻👏👏👏
Thank you so much for this, I've been trying to wrap my head around it for years.
Jimber Jam what a perfect comment. Thank you. Let's me know I achieved what I set out to do, and made it nice and clear. :) :) :)
Definitely! I have been shooting exclusively on the GH4, and have gotten a 'feel' over the years, between my native lenses and speedbooster and Canon glass.... but I've never been able to really grasp it, (or explain it to my colleagues who shoot on the FF cameras like the Ursa Mini) and certainly not to explain it to someone else (which is, in my opinion, the true measure of understanding something).
Wonderful video, and a happy new sub from us!
Thanks! I will have a good nose at your uploads later on tonight. (I subbed, so will catch your new ups too)
:| Don't go back too far! Haha!
I had to stop this video now. Not to tell you that "I don't understand what you are talking about", but to say that each time I am to some degree confused, you address the subject and get me right back on track. This has seriously! got to be one of the best informative videos I have ever seen. The hat is off to you, sir! Amazing
Thanks for doing this video! I've done some FF vs M43 DOF tests and didn't know why the ISO was so different for the same exposure, until now.
Nice one Louis, exactly the kind of thing i like to hear. :)
(Lets me know I am being helpful)
p.s. if you were getting the rest of the equivalence right, and just not the ISO, then you are still doing better than the majority of people I chat to on the Facebook groups... :) They just do the focal length, get bad results, then say the sensor it crap! (doofasus!)
Reminds me of the science class on light reflection back in middle school! Thank you so much.
This has swayed me to keep my m4\3 cameras and lenses. Great explanation!!
Matthew Peer I love both (m43 and FF)
Gh4 prob gets most use.
But a7s comes out at night. :)
Also playing with medium format now too.
Fun to tinker.
Great stuff, will check the follow up vid, but already a huge thanks for clarifying this complicated subject... been shooting stills for about 25 years (about 10 of those professionally) and only now I have at least a good understanding of the matters (and math) behind all of this! Thank you, Sir!
This was, put simply, AMAZING! Thanks!!!
Your information at 20:35 is spot on! I was JUST about to do a video on this. Everyone explains how to calculate the focal length as far as different sensors go, but they ALWAYS forget one factor. Distance. You don't need to make equivalencies if the phone ISN'T composed the same way :)
Wonderful video, thank you :) Just wondering at 25:45, what about distortion? Will the m43 wider lens have different compression / distortion characteristics compared to the 85??
Thank you so much man ! You explained it so well accompanied with perfect examples on the go. There’s so much confusion about this stuff but when you think about it from the mathematical point of view, it all starts to make sense. Cheers dude! Keep up the good work.
4 years of doubts were explained today. thanks a lot!!! great work
:D ... look out for a newer more in-depth version of this coming soon... covering ISO equiv and speedboosters etc with more practical tests to back up the maths. :)
(I'm half way through it, but its taking a while as i need to keep finding very specific lenses to do it properly)
Hats off bro! Nice and concise. Keep it up. Need more info like this.
best explanation and diagrams of all these concepts that I have found on YT so far. thanks big time.
Does this apply also to the opposite - to get deeper DOF on a crop sensor I can use more open aperture?
I have searched for this knowledge for a very long time. Thank you very much!
Well done.
I have a hard time getting my head around something until I understand it intellectually.
Thanks for that.
Thank you very much for this video. You have opened my eyes and brain.
Amazing explaind! I`ve a question :) Do you know or there are some formulas to calculate this different factors or put them together? (And then especially with the sensor size itself)
I am now pointing all my friends that ask me questions about this to your video. This is probably the best lesson on it out of every technical video on TH-cam. Thanks so much for taking the time to make it :)
Thank Brian. I may well re do this vid to perfect the message (couple of tiny mistakes) but i think it does a pretty good job of combining everything people need to know.
It does a great job. The depth of field discussion alone makes it more than worthwhile. You may not realize this but in the midst of your physics discussion you showed how depth of field works as a tool for the aesthetics of a given photo. Until aperture is seriously understood like this you can end up fiddling around with 100s of photos before you understand it by accident...LOL. The sooner you realize DoF the quicker you can leverage it in your photography. I was one on the people who spent months fiddling with it without this level of understanding. After much trial and error combined with piecing together bits and pieces from TH-cam that is actually self-containted in your video, I finally understood it a few years ago. It's so refreshing to have your video on it that it should be posted everywhere. I'm just glad PetaPixel pointed everyone to it. Bravo sir ;)
High praise indeed. thank you.
I make no bones about the fact I learnt much of this from filmmaker IQ and Tony Northrup. But I wanted to try to combine all of those elements, and also help it be more visually literate with the simple illustrations.
(For those of us that don't think in math equations) :)
I just want to say thanks for the engagement on this video folks! Apart from a very 'shouty' minority on the forums. Most people get it and agree.
I think the really clued up viewers already knew this stuff anyway, but I think also a fair chunk of you learned something useful. In which case Im glad the video did its job.
And I would like to again remind you to check out Tony Northrups, and FilmmakerIQ channels.
As I myself learnt a great deal from them, and hopefully wrapped it all up for you into this one vid for you.
I've seen Tony's take on this and the current video which largely corroborates the same points.
It makes sense to me that total light captured is important since we are blowing up pictures to the same display medium (screen or print).
It seems like common sense to assume that the light 'wasted' by the cropped sensor not capitalizing on the full image circle projected by the lens would incur a penalty since we are losing "optical resolution".
One thing that does intrigue me about the Angry Photographer's take on this is that he insists it is wrong to assume that bigger sensors are like bigger solar panels and consequently no penalty actually exists for cropping (does this mean that the part of the image circle that is captured still yields vastly greater optical resolution than the photosites available to capture it and "wasting" light by cropping stills leaves plentiful optical resolution anyway? - I'm confused...).
Angry's point is also that a lens does not care what sensor lies behind it, but I don't think either Tony or biscuits contradict that statement.
It would be nice to have them openly debate about this. :-)
Mark Pitsilos it seems to me you get everything you need to know to understand all of the major points in the vid. I'm kind of too tired now tonight to give any any more feedback regarding the some of the minutiae side details.
So il leave it there, and pick up any remaining loose threads tomorrow eve..... Night!
just skimming the comments again, regarding that angry guys take on it, I'm confused as hell by his comments, he keeps changing his mind as to exactly what is wrong with the points in my video.
And once i realised he was unhinged i have now ceased all communication with him and blocked him on every platform he shouts and spits nonsense in. :)
(one of the biggest nutters i have EVER met online. without a close second, he spammed me with so much crap you would not believe it.)
but regarding the 'not working like solar panels' argument.
This makes no sense to me.
The only way his argument would hold any water at all is if, when a manufacturer scales up the sensor size from one type to another, they keep the actual photosites the same size, (now with each 'pixel' having a tiny gap around it). But obviously they don't do that, because they want their sensor to be as efficient as possible. so they cram as much light sensitive surface area into the sensor as possible, wether its big OR small.
the signal to noise ratio is what its all about.
just like in audio, if you have a weak input and add a ton of gain you get crappy results. (the noise floor is raised etc.)
A image sensor simply needs as many photons as possible to give us that strong SNR.
and when you make the blooming sensor smaller, it has less photons hitting it.... like, no sh*t sherlock.
Even a child could see this as perfectly logical.
And considering all of the DXOmark testing data, and all of the practical experience from anyone that uses several sensors sized cameras will tell you. the sensor size has a DIRECT relationship to image noise.
As you probably already saw from TonyN vid-
'Crop Factor 4: Debate with a Critic & New Sensor Performance Data'
The sensor size has way more sway on image noise than even technology improvements over a few years span.
And even when you compare the very worst performing camera to the very best in a particular year.
Size still wins that particular arm wrestle time and time again.
So why he (angry fat dude camera guy theo or whatever his name is) can't see the wood for the trees despite everyone around him pointing to the mighty oaks all around him and telling him he's in a forest I have no idea. :)
best vid i've seen on this so far. great job!
Thanks William, glad it ticked a few boxes for you :)
Amazing video. Nice to see someone doing more than just scratching the surface of the subject, but at the same time making it easy to understand what he's saying. Subscribing.
Nice to hear, thanks.
@@biscuitsalive It's nice to see what's written, or just to read. Hearing that is something else altogether.
Very useful video, thanks! Learned a bunch of stuff I'd no idea about before :)
Rowan Lacey really appreciate that.
With such a contentious and potentially confusing topic, positive comments/feedback really are useful to hear. Then I know I made it all nice and clear. :)
Very, very interesting. Thank you.
This is amazing! You cleared a bunch of confusions!
Kang Du glad it helped. Lot to digest in there.
Very well explained. I knew a lot of the theory, but didn't know why or how. I think the only subject I didn't know about previously was circles of confusion. Your diagrams really helped. I watched a Tony Northrup video on the same subject recently. What he says is basically the same as you, but he doesn't explain why or how. To do this, the diagrams are essential, which is why your video is a better resource. The subject gets very technical and there's a lot to take in. Some people are very keen on the technical stuff purely for the sake of being technical, whereas I just want to have enough knowledge to help me take photos. I now need to watch the follow up video.
also - when talking about DOF being slimmer on an m43 lens, how are you calculating your math there? I was always taught depth of field is related to: focal lenght, aperture, snesor/film size and then obviously distance to subject. is there some shift in the math now that you're going from photochemical to pixel? or were you speaking just in terms of using FF equivalent numbers in regards to focal lengths?
This is one of the best explanation video I have ever watched. Nice job and thank you !
glad it helped :)
Damn, that soldiers analogy... I wonder how physically accurate is it considering the wave form of the light ray. Great video by the way!
Awesome info you shared here. Thank you.....
glad you liked it. :)
I have been a photographer for a 5 years now and do a lot of reading and watching on the subject. This is the first time I have had aperture explained to a level where I can understand the mechanics of how this works, not just the effect.
Pete B cool! That was my goal. To explain literally what’s happening in your lens as simply as I could. (But still covering a lot of information... it’s a tricky juggle)
Be sure to watch my follow up vid.
As I did make a couple of minor mistakes in this vid that I wanted to correct.
I am an engineer so always want to know the specifics of how something works. I didn’t review the FF vs Crop and ISO parts, as I am always fairly confident in that area. Will look out for the update.
here is the link, its a bit boring, but i like to correct my mistakes if possible - th-cam.com/video/fCIWkqcb7FI/w-d-xo.html
Thank you for creating a wonderfully explained and illustrated video on this topic and doing a Follow-Up video. I'm working on a similar video to create more awareness around what makes the IMAX look and why it's not as unique as it was in its digital infancy.
12:50 why doesn't the light go to the edges of that element and then the elements diffracts it to the center of the image sensor to create a wider image while maintaining the shallow depth of field?
Excellent video! Great explanation. I found your video looking to more explanations or discussion after the Tony's videos. I simply don't understand why detractors didn't understand or are confused with such basic concepts for a serious photographer. Other interesting aspect is that nobody have provide a single image to show the contrary. Great job.
Claudio Rivera thanks! Yes it's crazy why people still argue this stuff. Especially when it's not difficult to spend a hour or so playing with a couple of cameras and see practical results that
Back up the theory fairly easily.
As I said in my vid I learnt a fair bit from people like Tony N myself, and I wanted to take it a bit further and look at what's happening inside the lens with my little
Illustrations. And it's always good to practically test these things yourself to understand things better.
One important thing I would add to the video though is the fact that when you shoot full frame, you need to get closer to your subject to get the same subject framing, with everything else being the same. So in your image comparison between the FF and the M43, if you moved in closer with the FF to match the framing of the M43, the DOF would be much smaller in the FF than the M43. This is where people realize that when they shoot bigger subjects like people, and they want an even shallower DOF WITH the same framing, a FF sensor suits them better. And yes, you could use a smaller f number on a lens with a cropped sensor to match the FF in this case, but if you are already shooting f1.8 on a cropped sensor, and want an ever shallower DOF, for the same framing, you will be hard pressed to find a lens f 1 or thereabouts. So the key is keeping the FRAMING the same when comparing FF and cropped with everything else being the same. Fantastic video though, I would have loved to see the differences when getting closer with the FF though.
Moving toward or away from the subject completely changes the field of view and introduces background compression or expansion into the equation. It will absolutely change the framing. If you compensate with a longer lens (multiplied by crop factor) on a full frame, you can achieve the actual exact same field of view as a cropped sensor. Crop sensors are ***not*** reaching further. They are just filling the frame with “more subject,” by cropping out the edges of the full frame equivalent. In the photos at 19:35, if you physically moved closer, you would change the relationship of the foreground and background subjects, changing the framing entirely. But what actually happens if you shoot from the same distance with the same lens, is the crop sensor is just a smaller piece of the larger picture. There are cases where either format can be advantageous, crop sensors do have a pixel density advantage which simulates “reach,” but you are correct that full frame does offer more flexibility with shallow depth of field and light intake assuming equivalent lenses.
I get it, but I'm trying to find out why my Canon 80D with 18-135 kit lens doesn't have a big depth of field when I have zoomed out. I was suspicious of it not doing this over the last year, so yesterday I did a DOF test on a long row of railings posts, so I compress them by zooming out. I first stood close to them and did around a 60mm focal length, I focussed a third of the distance in to the shot and tried at f8, f11, f16, f20. I know you get refraction with this lens after f11, but it was a DOF test and I still couldn't get everything in focus front to back. It did improve, but still the near and far posts were blurred. I then went around 24ft away from the end post I was stood by and zoomed to around 125 or 130mm and still had the same problem. I thought at least by f11 or f13 everything would be in focus. Is this a fault of this lens, or is this normal, do I have to crop photos every time, or am I doing something wrong. Does this happen with every lens on a Canon crop sensor, because at the moment I can get bigger DOF on my old bridge camera with a tiny sensor, zoomed out at f8. One reason I went to a DSLR was for its much bigger range of aperture values and being able to get everything in focus when I wanted that.
2:14 why would the image be focused to singular point rather than whole sensor ? I feel this question is stupid be I would like to know
Think of it this way.
Every point in the focusing plane in the real world, is focused down to one point on the sensor.
As you watch further that is illustrated
I prefer; " more in focus", and less in focus, as you are correct in one sense there is a thin line in "focus" there always could be theoretically a more shape image .... defined or limited by the medium used.. so in reality there is a " field of focus", which is based on an math equation... or ratio .. which after all is where we get f stop and t stop.. so so much nerdiness here LOVE IT
Very clear, worked for me!
Franco Salomón (thumbs up icon)
Brilliant video very well explained and easy to understand and grasp
If you look up depth of field in Dofcalc for say 200mm @ f8 for APSC then change it to Full frame at the same settings then the DOF is actually wider on the FF setting. What is a speed booster?
Willnot Betracked what are you getting at here?
biscuitsalive Not "getting at" anything buddy - my first sentence was just a fact. Depth of field for the same focal length and aperture is actually shallower on apsc sensors than full frame (according to DofCalc). My second sentence was a genuine question - what is speed booster? I have never heard of that before. I wasn't trying to be disrespectful. 😀
Willnot Betracked ok, sorry i didn't mean my comment to sound like that, i was just a bit confused. The first statement sounded like you were pointing out something that countered what I said in the vid.
But it of course does not.
A speed booster or “focal reducer” is a very popular device many crop sensor users choose today to recreate a larger sensor FOV/DOF on their smaller sensor.
Look at “metabones” that is the market leader.
I use a XL .64 speedbooster on my GH5
And it means I can use my full frame lenses on my m43 camera and achieve the same FOV and DOF as a APS -H sensored camera.
(I can use longer lenses and keep the framing)
Basically it regains the lost light that would spill around the smaller sensor.
So the image is brighter too.
(1.5 stops faster with my XL)
biscuitsalive Ok, thanks. I'll take a look at this metabones thing! 😀👍
they are expensive, but are amazing. the total light gathered from a full frame f2 lens is 4 times the amount gathered by a native M43 f2 lens. so its a awesome to be able to tap into most of that available light on a small /crop sensor camera.
Very nice! A lot of work you have done respect!
Some Thing thanks! I got fed up with arguing with people in camera groups about this stuff so thought I would try to clearly explain everything here.
biscuitsalive Thank you for that! You know what still some people dont believe but at the same time they dont give any evidence just noice. I think you know what kind of childish behavior I mean.
From my understanding the focal length is measured from the convergence point not sensor plane to the lens element. Correct?
when the lens is focused at infinity, and its in focus, then the FL is the distance to the sensor, but yes technically its the distance to the lights converging point. (if there was no sensor there to project an image onto, then it would still have a focus length...)
of course I'm assuming the set up is correct with the way i described it, if you put a FF lens straight onto a m43 body with no adaptor, and the converging point was throwing behind the sensor, then the FL wouldnt be measured to the sensor... but then you couldn't use this set up anyway. :)
biscuitsalive biscuitsalive well the convergence point isn't necessarily the focal point. Otherwise as images came in and out of focus they would flip upside down and right side up again. The convergence point is where all of the light crosses and flips over. Let me re-watch the video and pay closer attention (in 35 min you can get distracted lol) then I'll return to the comments here. I did a similar video about crop factors. Maybe check it out and we can discuss.
not it wouldn't flip, all light throwing off back of lens is in lines that describe the image, upside down, if you skip to around 08:48 you can see what i mean, the OOF areas are not then flipping back up the other way, if you move the sensor nearer if just gets blurry, if you move it further away it gets blurry too. it doesn't also flip from upside down to right way up..... i think you are getting the rays that trace points of light (for one tiny bit of detail) mixed up with the entire image. its the tiny points of light that are converging to create a 'IN FOCUS' image... the entire image will be upside down any way, in focus or not.
il have a look at your vid later on. :)
This might end up as spam because of the link. But this is how i understood focal length to be measure. expertphotography.com/understand-focal-length-4-easy-steps/
I have a question, what about perspective distortion? I mean, by applying the formula you get two images equal in terms of fov and dop but the perspective of 85mm shall be always different from a 42,5mm? Am I getting something wrong?
are you talking about lens compression? if so, this isn't a factor, heres an article that explains why - fstoppers.com/originals/lens-compression-doesnt-exist-147615
wow, wonderful! Just a question. The cropped Iso related to the sensor does it also involve the noise level? In other words, in terms of noise level 800FF is equal to the 200 into 4\3?
Thank you for this video. You nailed it. Thank you for mentioning Filmmaker IQ. It's great. Thank you for the reference.
Great video. Very clear and teaching. Thanks.
Glad it was helpful :)
in your tests you said both ff and m43 sensors were using "native lenses' - which tells me if you're at 50mm on both (50mm ff and 50mm m43), the m43 FF equivalent would be 25mm, right? my main question is regarding aperture - the lens manufacturers have already given us the m43 focal length on our 25mm (and sometimes will advertise their FF equivalence), do they THEN need to also give us adjust aperture readings (t stops versus f?)
A focal length is a focal length. It does not matter what the format is.
Great video. Thanks and respect!
Very nice explanation. I have sent several M43 users to your video when they try to tell me their Olympus 300mm f/4 is a 600mm f/4. When I tell them it's a 600mm f/8 and they have to boost the heck out of their ISO to match FF...heads explode. The marketing departments of several camera companies feed off the misinformation out there. Small sensors always pay a price.
Yep. They are correct of course when they state their lens/ focal length/Fstops. It’s when they claim their full frame equivalent numbers they often lie on purpose.
Some companies even show the full frame equivalence lens next to theirs in the adverts.
Not pointing out they the image /depth of field is entirely different.
@@biscuitsalive Why the Engineering depts. always hate the Marketing depts... :P
biscuitsalive: Thank you for your comprehensive and useful video. I knew about the DoF and aperture correlation, but with different sensore type it seems to be a complicated concept. So I felt this, but I’ve never put this together. Now i understand better how it works. I would have 2 questions, and i I know this information is in your video, but really just would like to make sure if i get this right. I am asking this from an APS sensor user point of view. For me having a nice background blur on a portrait image is the most important. 1, fuji fx has 1.5 crop factor. If I would like to have the same blur than I have with nikon FF 50mm f1.2, I would need 35mm f0.8. There is no such lens on the market. Right ? Only thing I can do that I use a longer lens and step backward. Am I right ? 2, ISO has nothing to do with other feature of the image except noise level, isn’t it ? I am just asking because I am an APS user now. In order to get similar nose than I got with nikon on 100 ISO, I would need 44 ISO on Fujifilm APS. Again, there is no such sensor. So I guess the main differences show at the “lower end” of the parameter scale. On the other hand there are noise level differences between different type and brand of sensors. So ISO 400 dosn’t result the same level of noise e.g. sony and fuij APS. The noise is not only matter of size. Right?
I know this is a few years after this was first posted and am pleased to see someone get it correct, I have been so frustrated with the amount of posts claiming that sensor size changes depth of field, only subject distance, aperture and focal length change depth of field. I do however feel that there is confusion over the ‘circle of confusion’ and I do not see how it impacts the depth of field with sensor size. As you show in you diagram the point of focus is the size of a pixel and a sharp point, reducing sensor size but retaining the resolution creates the overlap onto other pixels. You state that this impacts depth of field, but I disagree, to me the circle of confusion will have the same effect across the whole sensor regardless of depth of field, it has an impact on the overall sharpness and not depth of field.
Thanks for taking the time for putting this together, got my first DSLR recently (I’ve only ever used compacts) and really disappointed the sales guy didn’t explain about the cropped sensor vs full frame, and, I can’t understand why Canon won’t label the EFS series of Lenses what they actually are considering they can’t be used on the FF, after watching this video and Tony Northrup I’m now getting better exposure with my pics
rawknroll Paul glad it was useful.
Yep a system that shows the FOV angle and the total amount of light let through would be much better than focal length and fstop
Thank you so much...
Mistakes are spotted :).
But, thank you so much for this detailed explanation.
Sameir Ali thank you Sameir.
Which mistakes? (Want to add annotations for any to keep the wolves at bay.)
I misspoke a couple of tiny times. (Saying complete when I meant compete near end etc.)
But I think it's still fairly clear what I meant.
But please do point out any specific mistakes so I can amend.
Sameir Ali and I would redo some of the illustrations slightly. (Apple too close to end of lens, and this muddied water for certain points.)
Also, the DOF area (yellow dotted line) should be stretching out so more area for "acceptably" in focus behind focus plane then in front.
But again that doesn't change the core message... but I should have factored that in.
All the mistakes are acceptable and understandable.
By the way, I think you said about square of 200 is 800, that needs to be corrected. What you said about the crop factor was right. So, the ISO is not be be squared. It should be multiplied with 4.
I have subscribed to the channel, and keep looking for more information.
Keep up the good work.
Sameir Ali no what I said was we square the crop factor for the ISO (I will re watch to check I said it correctly later... but certainly that's how I wrote it down for the illustration)
So our crop factor for the M43 to FF is X2
So if you get your calculator out and type out,
200 times 2 then press the squared button.
This gives us 800
If it was APSC it would be X1.5 (canon is 1.6)
So 200 times 1.5 squared = 450
So ISO200 on a apsc cam. And ISO450 on a FF would equal the same total light. And have equivalent noise.
Great explanation!
ObelixCMM thanks you!!!
Excellent stuff!
Great video. Thank you.
You explained wonderfully..
This is the clearest, most concise explanation of this subject I have seen. The key elements are succinctly outlined with easy to understand with illustrated explanations. The pacing is appropriate as well without getting overly bogged down in any of the steps. I've seen many videos and read many articles on this, but this video encapsulates these factors the best. Thank you. If I were to offer any suggestion, then I would recommend: 1) Using a larger colored cursor and moving it much less (the excessive cursor movement is very distracting) 2) For the text heavy slides, I would bring in each text section of the slide separately to help lead the watcher digest the information, instead of overwhelming the watcher all at once. With that said, the video is free and offered as a service, so I can't complain too much. I'm very appreciative for your effort and the time you took to produce it. The video is great educational service to anyone interested in the optics of cameras.
anglewinder thanks! And I agree on your criticisms.
I did this video in one take/recording after drawing the illustrations.
I should have spent longer on assembly.
But I tend not to put lots of work into TH-cam when I’m busy with paid work.
TH-cam is a fun hobby for me. Nothing more. :)
But if I have a quiet work period, you will see spikes in quality on my TH-cam content, simply as I then have more time to spend.
Fantastic video! I enjoyed the follow up as well. I have a quick ? on the circle of confusion and how it effects the other metrics when you take into account when sensor sizes scale, the resolution often changes as well. For instance a GH5 vs an A7RIII.
TheKoop117 yes in this video I was mostly talking about same res at diff sensor sizes.
(So 4k video as I mostly use)
Higher the pixel density the smaller the circle of confusion becomes.
But in terms of end product it still comes down to how it’s viewed.
If it’s printed huge and viewed close the allergens depth of field will become narrower. And visa versa.
So you do need to take into account the circle of confusion of the sensor/pixel density. AND the final viewing set up.
(Tv screen at 3 meters... cinema at 20 meters... billboard at 50 meters etc)
Very good explanation, thank you for clearing up some misconceptions. The most contentious issue for most will be the noise/iso relationship which will upset a lot of m4/3 and some aps-c owners. You need very much faster lenses to keep the sensor noise under control. As you say, manufacturers are realising that they have to be more honest about lens equivalence not only focal length but also max aperture. Camera and lens manufacturers should make speed boosters that are specific to their larger format lens ranges. I.e. Fujishould make one specifically for mounting full frame legacy Fuji lenses on their aps-c camera bodies.
Howard Maryon-Davis I agree.
And the point about the noise vs sensor size has the most variables to factor in. (In regards to each sensor technology/design etc)
But I believe it’s safe to say if you took two identical sensors (in terms of the technology, eg. Back lit/cmos/ Same res etc etc) but one is smaller than the other. Then you can use the crop factor squared to equate noise levels. (across the whole image. Bare in mind if res between sensors is different, and you judge image noise at 100% then the formula brakes down as the portion of total
Sensor is no longer equal. )
This is why judging 2 x 4k full width sensor images is a good/fair test to reference.
As even if one sensor is higher res. The down sampling to 4k helps even things up. (As long as using whole width of each sensor and not cropping like the gh4 does)
the output of the lens at the back of the lens ? whats if you not have the same lens with a different output size ?
good video very well explained
Hi .thanks for this awesome video. Most of my doubts have been cleared after a long time. Really thanks for taking your time. But I have one genuine query. Hope you will give me an opinion.
In my place, new gh4 body + speed booster is the same price as a new 6d m2 with kit lens. Lumix g85 is also a cheaper option. I'm on a very limited budget but want to make short films for TH-cam. I'm also doing colour grading, so a log format is a must. Please tell me which one should I look for.
I ve got a kinda weird question about shallow depth of field. Why panaosnic or olympus can't make the real full frame equivalent lens for a micro 4/3 body. If we adapt some full frame lenses with a speedboster, it continues to work as a full frame lens, with the same DOF, but with a slight crop. So, why oly/pana can't make the same lens but with the native autofocus? I'm shooting with a G7, and using some FF lenses from canon, only for DOF, I don't want to change the whole system, but I really want to get the FF DOF on my Panasonic body, without barely working autofocus from a speedbooster.
Are you asking why they don’t make a lens with a speed booster built in?
XD
It’s a good question I guess.
I don’t think it would fit with what they are doing when they choose a small sensor for their camera line. They specifically want small lenses for their small camera.
Part of the appeal for many people.
Plus they would be really expensive etc.
@@biscuitsalive lol, leica of olympus pro lenses sometimes as expensive as they FF rivals, and also they are pretty big, so that's why I am little bit confused, after watching this video, it looks like they just don't want to make it, and I don't know why. Panasonic ambassador told me that he also doesn't know the answer lol.
Finally!! Bravo!
Well Done! Thanks a bunch!
Wes Baker glad it was useful.
OK, so here is a list of mistakes so far. (thankfully all tiny, and not deal breakers.)
1. The converging light rays that fall slightly behind the sensor when it is focusing on a OOF point behind the apple,
(the purple light lines at 08:55 )
Sorry, I messed up the raytracing in my haste, they should have converged just in front of the sensor, not behind it. Totally my bad. And thanks for pointing that out.
But it doesn't change the main message for that section, the light rays converge just one side of the sensor surface, and not bang on it, hence being out of focus.
2. The Label 'Depth of field' above the sensor (in yellow) should say 'Depth of focus' Sorry this was just a typo, as I copy an pasted the other label while making my layout, and then didn't correct it.
(So its DEPTH OF FIELD in front of the lens around your subject, and DEPTH OF FOCUS behind the lens around your sensor. But again it doesn't change the message, just a typo. Sorry.
3. Not a mistake, but I just wish that I mentioned the COMPRESSION too. Just to assure you, If you follow the method I suggest in this vid, then you also match compression between diff sized sensors. This is simply because you don't change the distance to the subject. Several people asked about compression, so I just wanted to quickly mention something about that.
I watched the mistake film first. A very good real world set of examples.
robbyboyo cheers Robby.
Simply brilliant video. No fancy bullshit and down to the point.
Thanks for the feedback, be sure to check the follow up, couple minor mistakes in my illustration which i dress there.
Great and clear explanation. Tnx
timmerdude thanks. glad to hear that. :)
Firstly - thanks for the detailed explanation - 1 point about FF vs. APSC (or MC43), is the recent shift to cropped sensors with high count of MP, i.e., emerging 33MP APSC cameras rumored to come out the next few years - I would like to see this video updated to include the effect of such a shift (more noise - since less light per pixel, but maybe compensated since it makes a difference to the coverage of the CoC ? - And if so,is it pronounced enough to nullify the effect? -Under "low light"/ Normal Light ?
Thank you so much for this. It is so accurate.
I loved this video, finally someone took the time to explain this in a way I can understand. I have a question concerning native mft lenses. So say you have a 25mm 1.7 prime. That would be 50mm on full frame, but do you double the aperture of native mft lenses as well?
Daniel Strauss thanks. That's what I was going for. Explaining it a bit more visually (illustrations etc)
Yes. That's exactly what you do.
So a 25mm f1.7 M43 lens will perform just as a 50mm f3.4 lens on full frame.
This is why we need really fast lenses on M43 if we want to match the DOF and image noise quality of FF.
My fastest M43 lens is a 42.5mm f1.2
And that works exactly like a 85mm f2.4
(Lovely for portraits)
Or as you probably already know, u can use a speed booster and this gets you most of the way there, and use the same lens as you would on the FF. (But with a slightly tighter shot)
Daniel Strauss just a side note on this.
When you get a native crop sensor lens that completely matches the performance of a FF lens.
It will have to be as physically big as the FF equivalent. (Front element has to be big to let in enough light etc. )
So you can practically just eye ball the crop sensor lenses and tell.
This is why it's outrageous when a manufacturer states something like.
"24-300mm f4 equivalent" on the lens or fixed lens crop camera advertising/description.
When it's a actually a 12-150mm f4 M43 lens.
They should have said "24-300mm f8 equivalent." Then they wouldn't have been lying fiends! ;)
Thank you! I get it now. Yeah speedboosters help a great deal in achieving that full frame look on mft.
Okay so I have a question. After you applied the crop factor to the aperture, you ended up with the full frame image at f4 and the m 4/3 at f2. So of course these images look the same now. But with the full frame you still have the option to go to a lower aperture as opposed to the m 4/3 image you are at the lowest aperture setting (generally speaking if using a zoom). With that in mind wouldn't the full frame then be giving you a better depth of field?
29:20 of the video he explains that consumers are wanting lens makers to offer true equivalent lens options.
But, I understand that Canon's famous 50mm f:1.4 is going to be hard to replicate into a 32mm f:0.875 for my APS-C Canon M... or a 25mm f:0.7 for a M4/3.
Yes, FF wins. Makes sense though. Bigger is better. Always has been, always will. If you know what you are doing that is.
I have a question, if the focal length is just the distance between the lens plate and the focus point, why a FF 50mm lens is different than a APSC 50mm lens? Why do we need lenses for specific sensor sizes, and in which ways are they different?
William Chen it’s just the image circle size.
A physically smaller lens (smaller disc of glass/lens and housing) will create a smaller image circle behind it. So bigger sensor needs bigger glass element etc so as not to vignette.
@@biscuitsalive Ah that just cleared out my confusion! Thank you so much for your quick reply! If you would like to, I think you could make another video about the science behind "mounting a full frame lens on a smaller sensor (and vice versa)" and the pros and cons of doing so.
@@williamchen8009 no probs, ive been too busy with work to do any youtube stuff recently, but i do enjoying doing videos just for fun now and again
Thank you!!!! ;)
Excellent. This should (but likely won't) end all the confusion. Math doesn't lie. (And I secretly delight that this vindicates Tony Northrup, who has gotten way too much grief for being right). Thank you for taking the time to put this together!
Peter Lewis glad you liked it. :)
@@biscuitsalive Not only did I like it, but I learned a lot from it. Been a working pro for over 30 years, but am still constantly learning things, and your video was so precise and clarifying. Your combination of science, math, and real-world examples was extraordinarily helpful. You're helping to clear the fog away!
Peter Lewis nice to hear!
Very nice and easy explanation. The main reason that people say that FF has more bokeh is because the lens for crop sensors are not fast enough to compensate for the crop factor. If they make 25mm f 0.9 with autofocus on MFT it will compete with the standard f 1.8. If they want to compete with the f 1.2 lenses they will have to do some serious engineering to create a lens that has an apperture of f 0.6 .
But the speedboosters are a very good solution until they come up with super fast lenses for aps-c and MFT.
Let's hope they stop the marketing BS with the crop factors. Best solution I can find to clear the misinformation is to list the focal length as they are but to include the equivalence for the crop factor.
Thanks i learned a lot from this video! Thank you!
quick question: Is the hurdle a lower base iso, or higher base iso? Would have guessed the iso is already higher, being equivalent to a high ff iso. Correct me if I am wrong. Great video.
Julius Herrmann the hurdle for smaller sensors in optimum conditions is lower base ISO. To match image noise of full frame camera at ISO100 a m43 needs to be at ISO50 at most.
But new sensor tech will no doubt change all this soon. But there is always going to be an advantage to larger sensors. Most noticeably in bad light /high ISO range.
I really enjoy watching this video, which teaches me a lot. However, I have a question, you said smaller sensor has shallower DOF. I want to clarify something. If I take two pictures with same lens at same focal length, same aperture and same distance to the object but one use full frame and one use APSC(1.5x) . The final image of APSC one would have a shallower DOF compared to the full frame one? that means if I scale up the full frame image 150% ( assume the resolution is not a matter), these two pictures would be different in DOF? Please correct me if I hv some misunderstand. Thank you very much
Yep it’s a bit confusing.
It’s technically true that if you take a FF cam and a crop sensor cam, put the same lens, at same aperture at same distance to subject.
The crop sensor camera will have a shallower DOF (and will be a tighter framing). But only in the same way that if you take the FF shot, and cropped into the centre of the shot.
What people forget is that DOF is not a set parameter, it’s a sliding scale.
And if the image is at higher res, or enlarged then the amount of the image that is clearly sharp is lessened.
This is apparent to us all, but we sometimes don’t make the connection.
Eg. a shot looks sharp when viewed in the EVF. But then we get home and inspect it on a big screen and we see we missed focus.
It looks sharp small. But soft when big.
This is the same for cropping in (what a smaller sensor naturally does)
When you crop into the centre of shot you are enlarging the image, and any “slightly out of focus” area now look MORE blurry.
That’s the subjective side.
Then there’s the technical side too.
That’s down to the circle of confusion.
The pixels are smaller on smaller sensor. (If both FF and crop sensor have same res)
So the out of focus areas are MORE out of focus. The DOF will literally be shallower on the smaller sensor because the point at which the light points overlap the pixels, and blurs across 4 or more pixels is when we can detect something isn’t sharp. We can not detect any blurs tighter than something one pixel across.
You have to remember there is only ONE plane technically IN focus. Even at small apertures.
The rest is just slightly slightly slightly out of focus. But we can’t tell because it’s within our one pixel limit (or photosite to be accurate)
If any of that is unclear.
Maybe investigate “circle of confusion”
@@biscuitsalive Thanks a lot, its a great video
I have read many times of what you said, after that, can i say a lesser density of a senor will have a shallower DOF than a higher density sensor? Thanks
Excellent video.
Serge Pilon thanks Serge. A few polite positive comments filtering through the shouty ones from people that don't get it yet. :)
At 17:00, the difference between sensor size accounting for the shallower dof on a smaller sensor has nothing to do with pixel size. The difference is because for a relevant comparison (same sized output) the smaller sensor output is magnified more, ergo it demands a smaller coc on the sensor to attain the same output size/coc relationship.
Pixel size has nothing to do with any of this, nothing at all. Magnification, and the fact that you need to magnify a smaller sensor output more than a larger sensor has everything to do with it.
Scott Ferris I sort of agree with you.
It's not about the pixels really, but
I was using a few pixels simply as an example as to why the CoC could be considered OUT of focus on one sensor, and IN focus on another (even with exactly the same lens, same aperture, same distance to subject. )
Let's forget resolution differences between the sensors, and say we are filming 4K video on both sensors. (More like how I would use them in practice anyway)
The 4K on the crop sensor obviously has narrower tolerances for what is acceptably in focus ,and what is acceptably out of focus.
Due to the CoC.
So that's why I used the pixels to explain the difference. (Personally I thought it was a nice clear way to show this. But obviously you disagree.)
Anyway I don't think you are arguing with the overall point I was making at all. You just don't like the way I expressed my point.
Of course you agree, my comment is accurate :-) I understand what you were doing, the problem I saw was you never mentioned magnification differences, which is absolutely key to understanding the differences we see, and presented that issue in the terms of pixel size, that will lead to confusion and inaccurate understanding of your otherwise excellent video.
The site that explains it all in as much detail as you could ever wish for is here www.josephjamesphotography.com/equivalence/
I am definitely not arguing with your point, just hoping you could add an addendum to point out that critical element of the equation. The magnification 'thing' is so fundamental to photography, and is never talked about, how many people acknowledge or understand that when you crop an image and view at the same size you lose DOF? Once you understand that getting f1.0 dof in your portraits isn't difficult or expensive, just maths :-)
Scott Ferris I think the fact I shrunk the sensor down does clearly show the magnification. (Just sort of inverted)
Anyway. Glad you agree in principle.
Certainly there are ways I could have described some of this better.
I really should have wrote a script.
But decided just to reasearch the facts for a few days. Then start recording. :)
Clearly not the best way, but it's the quickest.
(One take wonder)
Scott Ferris I may make a "proper" version. With tighter structure and fully animated illustrations.
(Less power point like :D )
If I have time of course. Probably a weeks work to do a high production value version.
So I'm calling this one the alpha version. :)
To be sure, the only reason I made an account and posted for the first time ever is because you specifically ask people to at the end of your video. Not emphasizing the fundamental nature and impact that magnification has in an equivalence explanation is an omission of some note.
I applaud your video, and your need for tea at the end :-) but wish, very much, you had included that element.
Great way of simplifying and therefor clearly explaining the differences and similarities in gear usage and the final images aimed at. Every pro should know. Thanks for sharing your knowledge about the subject!
Beeldproducent - film-video-foto I tip my hat to you sir!
Great, now that I got all that, I will get mad at people that say wrong things about it, even professional photographers on TH-cam and such 😑. Your fault.
Haha seriously now, thanks a lot for that video!! I actually just came across it, wasn‘t searching for it ... but DOF in relation to crop sensors was definitely something I came a cross with a lot! So happy to understand it now! :)
Fabio Mota glad it was useful. :)
I've always liked that analogy about a marching army walking from a hard surface to a soft surface. I think you can take it a step further though. If you imagine each line of people is a different wavelength of light, the higher the wavelength the smaller and faster the gate of those marchers. So all the marchers are marching at the same speed, but on one side you have people taking large slow steps, and on the other side, people taking small fast steps. When they reach the sand, or mud, the people taking big steps get further into the mud before they are slowed down by it, and those taking small steps don't get as far before they are slowed down. That causes the marching lines to diverge from each other. I theory they should begin to converge on the other side of the "lens" but I think that could help explain chromatic aberration.
Grant Pluntze nice one! Yep that works lovely. I could see that working in a animation. :)
Grant Pluntze Dec
This is a wonderful video. I now understand the physics behind applying the crop factor to focal length and aperture. However, I don't understand the physics behind applying the applying the crop factor squared to the ISO other than it is an area rather than linear. First, I assume I could decrease the shutter speed by say two stops rather than increasing the ISO by two stops. Is that correct? Second, what happens if the full frame is 50mp and the ASP-C is 24mp? It seems the crop factor should be applied to the focal length but now it is less clear what I should do to aperture and ISO. biscuitsalive, I would appreciate your comments.
Thanks.
Yep it is a bit confusing.
So what I’m getting at regarding applying crop factor squared to the ISO is that then completed the full equivalence.
So CF to focal length makes FOV the same.
CF to aperture makes DOF the same.
CF2 to the iso then makes exposure match.
As you’ve closed down the aperture on the full frame camera we are getting less light in the camera.
So you have to up the iso to match exposure.
And remember it’s surface area we are talking about. As the FF sensor is 4 times the area of the mft sensor. So if each pixel is to be getting hit by the same intensity of light (across the whole area) then you need 4x the light falling across the whole sensor.
(Imagine if you took a magnifying glass and focused the light down onto a smaller area. It’s the same total light entering the glass. But it’s focused down into a smaller area. This is kind of what we need to do.)
The thing that confuses everyone is they think of ISO as a “sensitivity” but it’s not really it’s gain. And that gain is calculated per square inch (sort of).
So iso 400 on a small sensor isn’t really the same as iso 400 on a big sensor.
Iso 200 on a m43 sensor is technically more like iso 800 on a FF sensor.
This is why it all fits together perfectly when you follow my full equivalence.
Because (to answer your second question too) when both sensors are THE SAME RES. The. And both technologies are about equal. The FF at iso 800 will have same image nose as a m43 at iso 200.
So yes if one has completely different res this does completely change everything.
Just as if 2 camera with identical sized sensors has one high res and one low res.
Generally speaking the lower res camera has less noise.
But again this is debatable too.
If you took 2 FF cameras one 52mp and one 12mp (same technology just diff MP)
Then if you looked at a 100x100 pixel area of both the low res sensor would be much cleaner.
BUT if you looked at the entire image.
From the same distance.
Chances are image noise would be very similar. (Some small advantage to lower res sensor due to packing in less technology into small space)
So this is the thing.
For me who generally shoots video.
And nearly always at 4K
The lower res sensors. (Like a7s2 Or gh5s) has the best chance of low noise.
But for photographers it’s a bit debatable.
Pixel per pixel lower res sensors have less noise than higher res.
BUT THIS IS JUST BECAUSE THE ACTUAL INDIVIDUAL PIXEL (photosite) IS LARGER.
Sorry to shout. Just that’s something that many people argue about so I feel it need capitals to drill the point home to any of those guys that may be reading this. :D
Wow. I appreciate your fast and detailed response. Thanks.
I take a lot of bird photos in the wild with my Canon 80D and was considering the Canon 5DS. Using the same 400mm lens, the 5DS could possibly give me comperable bird photos but then dynamite full frame photos for landscape, etc. Probably not worth the price and the slower frame rate. Thanks again.
glasairdriver no probs. Hope my response made sense. Often type faster than my brain. :)
I’m still loving my Sony a7iii for stills at moment. (With canon/sigma lenses)
But I’m more of a video guy than a stills guy.
Anyway. Happy snapping.
Thank you so much. This video explains a lot. So what's the point of having MFT? If you need to do all that math every time, get a speed booster.
I have GH3 and thinking about getting a FF Camera.
This is the best explanation I have seen on this topic. Nevertheless, I think it is a mistake to say we make the three adjustments and get equivalence. That's just about as wrong as all the other explanations I see online in one sense. Now, it's true that those three adjustments will make the images very similar. But much of the time it's not even possible to do that. Suppose I use a 85mm f1.2 lens on full frame. Those are common today. Where do you find a f0.6 lens? They don't exist. Let's use an f2.8 100mm lens on full frame. So we need a 50mm lens at f1.4 for mft, which is likely doable. But now, our full frame camera has native ISO of 64. How will we replicate that? And a terrible misunderstanding comes from saying we double the aperture for micro four thirds to get full frame equivalence. That is because aperture is a physical measurement, and using a crop factor multiplication causes another myth because people think that aperture is really halved. But if that were true, we would need to double our exposure. But exposure times are correct. So, while it's true that if we adjust all three of those factors, it's rarely possible to do it in places where it's important. And people often think that statements like "halve the focal length" or "double the exposure" are true stand alone. It is therefore important to explain that these changes are not true when taken one or two at a time and very often they are not achievable. My explanation is that there are ways to make similar images if we intentionally handicap one system or another, but there is not a general way to create equivalence. Sometimes it's the crop sensor with an advantage. Consider a 400mm mft prime lens at f2.8. It has a magnified image so that full frame camera will need a 800mm lens for equivalent field of view. Now it's the full frame lens that can't match because nobody makes an 800mm f4, and if someone did it would be so heavy and expensive that nobody would buy it. True, the bokeh would be different, and there would be more noise. But you could still take pictures in low light because the f2.8 gives real exposure times. Maybe the subject is so complex it can't be made simple, but I have seen a lot of misunderstanding caused by explanations which use all three factors. Don't get me wrong. Your explanation is more clear and correct than any other I have seen. And if we are careful, we can get a correct understanding. But I have seen similar explanations cause as many misunderstandings as the outright myths.
thank you for your explanation, it helped a lot and i must say mft sensors are very very good, f. e. em1 II is likly even with a sony a7 iii sensor...
but ...
FOV + DOF + Aperture is what counts for me and i like the look of FF more.
even though i have canon with less accurate sensor.
Its a real shame that theres content out there that has a fraction of the effort put into it, and get millions of views where this gets just 89,000. A real shame. Youve explained how the aperture works like none other.
50mm (for a full frame lens) is roughly a "sweet spot" in terms of front element size. Assuming you keep the aperture the same, at shorter focal lengths you need a larger front element to accommodate the wider field of view, and at longer focal lengths you need a larger front element to accommodate the larger physical aperture size.
Physics is fun! :)
I was looking such a good explanation of dof for many years. Exceptional work. Many "photographers" fill up the TH-cam servers with stupid videos and all of them say the same obvious things. Aperture , shuter, iso blahblahblah. You took it the core where it needs to be taken. At some point we need to learn why things happen and how in photography. Great work.
You simply rock ! Good job man
George Karamolegos thanks buddy. :)
Why would the apple at 13:47 only use the middle of the lens?
Great video and excellent explanation. Wish you would have mentioned the lens compression too :). According my understanding it totally depends on the physical distance between the camera and the subject, therefore on an equivalent of 85mm (56mm or so) on crop body the compression would be same as on a real 85mm on full frame body. Please let me know if I am missing something.
Haider Abbas I was just thinking that last night!
(That I should have mentioned compression)
Yes, although I haven't tested for that personally yet. (Always like to test things physically before accepting anything fully.) I agree that it's just down to distance from subject.
Makes sense and it's just the relationship between one object overlapping another from a line of sight. And the FOV of course.
As you get further away from the subject.
(Say an actor) but the FOV angle shrinks. (To keep framing the same on that actor)
So we see less and less of the background scene. And the actor is also actually covering less and less of that background. (Not as important, but worth noting.)
This obviously does the same thing to everything that is at difference distances from the camera.
(This is why face distorts when using very wides lens, up close. And the same face looks flattened and more orthographic from a great distance with a very long lens. )
Anyway, good point you made.
There's a good chance I will revisit this topic again in a future vid, as I have learnt a lot from all the feedback I got from everyone.
Both about things I should have said.
And ways to make the trickier parts even more clear.
Not to mention I would like to add some raw independently gathered data that further proves some of the still disputed statements. (By a small but very vocal minority.)
:)